Buck converter with demagnetization detection of the inductor

ABSTRACT

A buck converter is equipped with a switch, a diode, an inductance, a capacitor, an input with a first connection and second connection, and an output with a first connection and second connection. The first connection of the input is connected to the first connection of the output via a series circuit comprised of the switch and the inductance; in particular, the switch is provided on the input side and the inductance is provided on the output side. In addition, the cathode of the diode is connected to the connection between the switch and the inductance while the anode of the diode is connected to the second connection of the input and to the second connection of the output. The capacitor is connected in parallel with the connections of the output. It is possible to trigger the switch by combining a first signal with a second signal and a third signal corresponding to a control variable from the output of the buck converter may be used to adjust the output signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a buck converter, a triggering method, and ause of the buck converter.

2. Description of the Related Art

Power supplies, in particular switching power supplies and switched modepower supplies as well as primarily and secondarily clocked switchingcontrollers are known from [1]. Every electrical power consumingcomponent requires a supply of electrical power, which is provided by apower supply and/or a power pack. Throughout the world, power lines areused as transmission lines in order to supply current and voltage to avirtually limitless array of electrical devices via electrical outlets.To this end, standardized alternating currents, e.g. 120 volts in theUSA and 230 volts in Germany, are customarily supplied via the powerlines.

In power factor correction, power consuming components in the circuit,in particular capacitances and inductances of a circuit, are compensatedfor through an appropriate wiring. Capacitances and inductances areprovided, which act in opposition to the capacitive and inductivecomponents of the circuit, thus largely compensating for them. Withregard to the topic of power factor correction, the reader is referredto power factor correction at www.tpub.com/neets/book2/4k.htm, forexample.

A power supply, e.g. a switched mode power supply, with a nonlinear loadcharacteristic generates current harmonics, even when fed by a purelysinusoidal supply voltage. The line impedance generates harmonics thatinfluence the line voltage and can lead to malfunctions. With regard toCE conformity labeling, it is necessary to test whether the productscomply with the requirements of the EMC law. Guidelines related to thisclassify both the permissible degree of electromagnetic interferenceemission and the resistance to malfunction in the presence ofelectromagnetic interference. The permissible limit values andmeasurement procedures for current harmonics are set forth in thestandard EN61000-3-2(also see EMV—Messtechnik [EMC Metrology]: “GegenStörungen aus dem Netz—Erfüllen Ihre Produkte die EN61000-3-2/-3?”[Preventing Interferences From the Power Grid—Do Your Products Complywith EN61000-3-2/-3?], Endress +Hauser eA, pp. eA 29, on the Internetat: www.zes.com/download/zes_sys6lk_presse_ea_(—)8_(—)01.pdf.

The object of the invention is to disclose a buck converter thatessentially conforms to the above-mentioned EN61000-3-2, and isefficient particularly with regard to the power factor correction. Thepresent invention also discloses a triggering method and several uses ofthe buck converter.

This object is attained according to the defining characteristics of theindependent claims. Modifications of the invention are disclosed in thedependent claims.

In order to attain the object of the invention, a buck converter isdisclosed, which is equipped with a switch, a diode, an inductance, acapacitor, an input with a first connection and second connection, andan output with a first connection and second connection. The firstconnection of the input is connected to the first connection of theoutput via a series circuit comprised of the switch and the inductance;in particular, the switch is provided on the input side and theinductance is provided on the output side. In addition, the cathode ofthe diode is connected to the connection between the switch and theinductance while the anode of the diode is connected to the secondconnection of the input and to the second connection of the output. Thecapacitor is connected in parallel with the connections of the output.The switch can be triggered by combining a first signal with a secondsignal.

It is thus advantageous that a combination or concatenation of the firstsignal and the second signal is used to trigger the switch. Because twodifferent signals or information sources are used, the circuit (the buckconverter) not only operates efficiently, i.e. provides an efficientpower factor correction, but also contains the harmonic amplitudes inaccordance with the standard EN61000-3-2.

In one modification, the first connection of the input is a positiveconnection and the second connection of the input is a negativeconnection. It is also possible for the first connection of the outputto be a positive connection and for the second connection of the outputto be a negative connection.

In a preferred embodiment, the polarities of the connections of theinput are reversed. In this case, the connections of the cathode andanode of the diode are reversed and in particular, the polarity of theswitch is reversed.

According to one embodiment, it is possible to trigger the switch bycombining the first signal with the second signal and a third signal. Inparticular, the third signal can be a control variable from the outputof the buck converter. The third signal can also be used to adjust theoutput signal of the buck converter. In addition, the third signal canbe a signal that is constant or that varies in an essentially slowfashion. Preferably, the third signal can be adjusted and/or regulatedby means of predetermined or predeterminable parameters. At least one ofthe following parameters or arbitrary combinations of the followingparameters can be used: output voltage of the buck converter, outputcurrent of the buck converter, or power of the buck converter.

According to one modification, the switch is comprised of at least oneelectronic switch.

In another modification, the diode is embodied in the form of anelectronic switch. In particular, in order to replace the diode with aMOSFET, it is possible to reduce the switching losses, particularlyduring an overload operation of the buck converter.

In particular, it is possible to replace the electronic switch with atleast one (bipolar) transistor, a field effect transistor, a MOSFET, athyristor, or an IGBT. It is also possible for combinations of theabove-mentioned components to be used as one or more electronicswitches.

In one embodiment, the above-mentioned combining of the first signalwith the second signal is an overlaying or addition of the two signals.

In one modification, the sum of the first signal and the second signalis compared to the third signal.

The first signal can be a current signal that corresponds in particularto the current flowing through the inductance or through the electronicswitch. The current signal can optionally be predetermined or determinedby the inductance. In this case, the triggering of the (electronic)switch is influenced by the current of the inductance. To that end, itis possible, for example, for an auxiliary winding of the inductance tobe provided, whose signal (current and/or voltage flowing through theauxiliary winding) is evaluated for purposes of triggering the switch.

It is also possible for the current signal to be determined through anintegration of a sum based on a voltage in the inductance.

In one modification, the second signal is an essentially triangularsignal or an essentially saw tooth-shaped signal. In particular, thisessentially triangular or essentially shaped-shaped signal can begenerated or predetermined by a generator, in particular a saw toothgenerator.

In another modification, the addition of the current signal and theessentially triangular or essentially shaped-shaped signal can beestablished through an integration of a voltage in the inductance andanother voltage. The additional voltage can be determined using a peakvalue rectification of the voltage in the inductance. It is alsopossible for the peak value rectification to be carried out with aretention time constant that is in particular (significantly) greaterthan the line period (e.g. by a factor of 5).

In another modification, an additional peak value rectification isprovided, which has a time constant that is in particular(significantly) less than the line period (e.g. by a factor of ⅕).

In addition, it is possible to limit the switch-on duration of theswitch, e.g. if the voltage in the inductance falls below apredetermined minimum.

In one modification, the capacitor is an electrolytic capacitor. In thiscase, its positive pole is connected to the first connection of theoutput.

The inductance can be embodied in the form of a coil, in particular athrottle.

It is also possible for a rectifier circuit to precede the buckconverter.

It is also possible for the buck converter to be used in a power supply,particularly in a power pack or a switched mode power supply. It is alsopossible for the power supply to be mounted on a mounting rail and/or ina switching cabinet.

A method for triggering the buck converter is also disclosed in order toattain the above-mentioned object of the invention.

The buck converter can also be used for limiting switch-on currentand/or for masking or suppressing transients.

It should be noted here that the term overvoltage is intended herein toapply to all forms of voltages greater than a predetermined supplyvoltage, in particular a line voltage, and all forms of voltage spikes.In particular, the term “transient” is intended herein to apply to alltypes of chronologically limited overvoltages that deviate from thetarget values of the electrical supply voltage. It should additionallybe noted that an overvoltage can also result from a current spike.

The buck converter can be operated in a single phase network and/or in athree-phase network.

The buck converter is particularly suitable for use in power factorcorrection.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be illustrated and explainedbelow in conjunction with the drawings.

FIG. 1 is a circuit diagram of a buck converter;

FIG. 2 is a circuit diagram of a switch in a buck converter;

FIG. 3 is another circuit diagram of a buck converter with a triggeringof an electronic switch;

FIG. 4 is an alternative circuit diagram of a buck converter with atriggering of an electronic switch;

FIG. 5 is another circuit diagram of a buck converter with a triggeringof an electronic switch;

FIG. 6 is a circuit diagram of a buck converter with a triggering of anelectronic switch and a peak value rectifier;

FIG. 7 is a circuit diagram of a buck converter with a triggering of anelectronic switch according to FIG. 6 and a peak value rectifier;

FIG. 8 is a circuit diagram of a buck converter with a triggering of anelectronic switch according to FIG. 7 and a limiting of the switching-onduration;

FIG. 9 is a circuit diagram of a buck converter with a triggering of anelectronic switch according to FIG. 7 with an alternative limiting ofthe switching-on duration;

FIG. 10 is a circuit diagram of a buck converter with a triggering of anelectronic switch according to FIG. 9, in which the diode has beenreplaced with an additional electronic switch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a circuit diagram of a buck converter that is equipped withan input (with connections 101 and 102), an output (with connections 103and 104), a diode D1, a switch 110 (with connections 107 and 108), aninductance L1 (with connections 105 and 106), and a capacitor C1.

The connection 101 of the input is connected to the connection 107 ofthe switch 110. The connection 108 of the switch 110 is connected to thecathode of the diode D1 and to the connection 105 of the inductance L1.The connection 106 of the inductance L1 is connected to the connection103 of the output. The capacitor C1 is situated in parallel with theoutput, i.e. it is connected to the connections 103 and 104. If thecapacitor C1 is embodied in the form of an electrolytic capacitor, thenits positive pole is connected to the connection 103 of the output. Theconnection 102 of the input is connected to the connection 104 of theoutput and to the anode of the diode D1.

Optionally, the polarity of the diode D1 in FIG. 1 can be reversed, i.e.the anode and cathode can be reversed. In this case, the polarity alsochanges at the input and output and also on the (electronic) switch 110.

FIG. 2 shows a wiring of the switch 110. FIG. 2 shows the connections107 and 108 of the switch 110 from FIG. 1. FIG. 2 also shows ann-channel MOSFET V1 (for example for an electronic switch), a triggeringunit 210 with a current control unit 220 and a generator 230, inparticular a saw tooth generator.

The drain connection of the MOSFET V1 is connected to the connection 107of the switch 110, while the source connection of the MOSFET V1 isconnected to the connection 108 of the switch 110. The gate connectionof the MOSFET V1 is connected to the triggering unit 210. The currentcontrol unit 220 supplies a first signal while the generator 230supplies a second signal. In the triggering unit 210, the first signalis combined with the second signal, in particular is added to it.

It is thus possible to overlay a current signal (e.g. an evaluation ofthe current through the inductance L1) with a saw tooth signal and thusto evaluate the combined (e.g. added) signal in the triggering unit 210and to trigger the gate connection of the MOSFET V1 (e.g. by using anadditional driver stage, not shown in FIG. 2). On the one hand, thisresults in an efficient power factor correction and on the other handassures that the harmonic amplitudes comply with those according to thestandard EN61000-3-2.

FIG. 3 shows another circuit diagram of a buck converter with atriggering of a switch. The circuit diagram in FIG. 3 includes a controlvoltage unit 310, a pulse width modulation unit 320, a driver stage 330,a MOSFET V1, a measurement resistor R1 (with connections 301 and 302),an inductance L1 (with connections 303 and 304), a diode D1, and acapacitor C1 (with connections 305 and 306 (in the case of anelectrolytic capacitor, the connection 305 is the positive pole)). Aninput (with connections 307 and 309) and an output (with connections 308and 309) are also provided (the input and the output share the commonconnection 309).

The control voltage unit 310 supplies a control voltage to the pulsewidth modulation 320, which also receives information from the measuringresistor R1 regarding the current flowing through the inductance L1.Based on these pieces of information, i.e. the control voltage and thecurrent through the inductance L1, the pulse width modulation 320generates a signal for triggering the gate connection of the n-channelMOSFET V1 via the driver stage 330. The drain connection of the MOSFETV1 is connected to the connection 307 of the input. The sourceconnection of the MOSFET V1 is connected to the cathode of the diode D1and to the connection 301 of the resistor R1. The connection 302 of theresistor R1 is connected to the connection 303 of the inductance L1,while the connection 304 of the inductance L1 is connected to theconnection 308 of the output and to the connection 305 of the capacitorC1. The connection 306 of the capacitor C1 is connected to the anode ofthe diode D1 and to the connection 309 of the output.

The current I flowing through the resistor R1 is needed to trigger theswitch V1. To that end, FIG. 3 symbolically depicts this flow ofinformation (via the current I) from the resistor R1 to the pulse widthmodulation 320.

FIG. 4 shows a circuit of a buck converter with an associated triggeringof the electronic switch.

FIG. 4 includes two comparators (Komp1 and Komp2), a pulse widthmodulation unit 410 (with inputs SET, RESET and an output 431), a driver420 (with an input 432 and an output 433), a control voltage unit 430, aprimary winding L1T1 of an inductance L1 (with connections 441 and 442),a secondary winding L1T2 of the inductance L1 (with connections 443 and444), a capacitor Cl (with connections 421 and 422), an (electrolytic)capacitor C2 (with connections 423 (positive pole) and 424), ann-channel MOSFET V1, two diodes Dl and D2, and resistors R1 (withconnections 411 and 412), R2 (with connections 413 and 414), R3 (withconnections 415 and 416), and R4 (with connections 417 and 418). Aninput (with connections 403 and 401) and an output (with connections 402and 401) are also provided. The connection 401 is the shared positivepole of the input and output. A reference voltage U1 is also provided.

The connection 443 of the secondary winding L1T2 is connected to thepositive input of the comparator Komp1 while the reference voltage U1contacts the negative input of the comparator Komp1. The output of thecomparator Komp1 is connected to the SET input of the pulse widthmodulation 410. The connection 444 of the secondary winding L1T2 isconnected to the connection 422 of the capacitor C1, to the connection418 of the resistor R4, and to the connection 403 of the input. Theoutput 431 of the pulse width modulation 410 is connected to the input432 of the driver 420. The output 433 of the driver 420 is connected tothe cathode of the diode D2, to the connection 411 of the resistor R1,and to the gate connection of the MOSFET V1. The anode of the diode D2is connected to the connection 421 of the capacitor C1, to theconnection 412 of the resistor R1, and to the connection 413 of theresistor R2. The connection 414 of the resistor R2 is connected to theconnection 415 of the resistor R3 and to the negative input of thecomparator Komp2. The connection 416 of the resistor R3 is connected tothe connection 417 of the resistor R4 and to the source connection ofthe MOSFET V1. The control voltage unit 430 supplies a control voltageto the positive input of the comparator Komp2. The output of thecomparator Komp2 is connected to the RESET input of the pulse widthmodulation 410.

The drain connection of the MOSFET V1 is connected to the anode of thediode D1 and to the connection 441 of the primary winding L1T1 of theinductance L1. The connection 442 of the primary winding L1T1 isconnected to the connection 424 of the capacitor C2 and to theconnection 402 of the output. The cathode of the diode D1 is connectedto the connection 423 of the capacitor C2 and to the connection 401 ofthe input and output.

Operation of the Circuit According to FIG. 4:

The resistor R4 is a measuring resistor for measuring the currentflowing through the inductance L1, which is measured in the sourcecircuit of the MOSFET V1. The current signal is combined with a sawtooth voltage ramp. The pulse width modulation 410 according to FIG. 4functions, for example, like a flip-flop. The (low active) SET input ofthe pulse width modulation 410 switches on the MOSFET V1 and the RESETinput of the pulse width modulation 410 switches off the MOSFET V1. Thecomparator Komp1 performs a demagnetization detection of the inductanceL1T1 by means of the auxiliary winding L1T2: through a comparison withthe reference voltage U1, the comparator Komp1 then switches on theMOSFET V1 (via the pulse width modulation 410 and the driver 420) oncethe inductance has been completely demagnetized. The delay while waitingfor the complete demagnetization of the inductance L1 (L1T1, determinedby means of the auxiliary winding L1T2) reduces the switching losses.

The saw tooth signal is determined in particular by means of thecapacitor C1, the resistor R1, and the diode D2; the resistors R2, R3,and R4 make it possible to overlay the current signal and the saw toothsignal. When the control preset that the control voltage unit 430predetermines by means of its control voltage is exceeded, thecomparator Komp2 switches off.

The connections of the output are reversed in comparison to thedepiction in FIG. 3 in order to simplify the potential ratios formeasurement of the current flowing through the inductance and thecontrol circuit.

For example, the control voltage unit 430 supplies a reference variablethat is determined based on a predetermined reference value and theoutput voltage of the buck converter. For example, if the output voltageof the buck converter deviates from the predetermined value, then thecontrol voltage unit 430 adapts the reference variable so that theoutput voltage once again corresponds to the predetermined value.

FIG. 5 shows an alternative circuit diagram of a buck converter with atriggering of an electronic switch.

FIG. 5 includes to comparators Komp1 and Komp2, a pulse width modulation510 with inputs SET and RESET and outputs 531 and 532, a driver 520(with an input 533 and an output 534), an n-channel MOSFET V1 and ann-channel MOSFET V2, a control voltage unit 530, an inductance L1 with amain winding L1T1 (with connections 513 and 514) and auxiliary windingL1T2 (with connections 515 and 516), diodes D1 and D2, a capacitor C1(with connections 525 and 526), an electrolytic capacitor C2 (withconnections 511 (positive pole) and 512), a reference voltage U1, areference voltage U2, and resistors R1 (with connections 521 and 522)and R2 (with connections 523 and 524). An input (with connections 501and 503) and an output (with connections 502 and 503) are also provided.The connection 503 is the common negative pole shared by the input andoutput.

The output of the comparator Komp1 contacts the SET input of the pulsewidth modulation 510. The output 531 of the pulse width modulation 510is connected to the input 533 of the driver 520 while the output 534 ofthe driver 520 is connected to the gate connection of the MOSFET V1. Theoutput 532 of the pulse width modulation 510 is connected to the gateconnection of the MOSFET V2. The drain connection of the MOSFET V1 isconnected to the connection 501 of the input. The source connection ofthe MOSFET V1 is connected to the cathode of the diode D1 and to theconnection 513 of the primary winding L1T1 of the inductance L1. Theconnection 514 of the primary winding L1T1 is connected to theconnection 502 of the output and to the connection 511 of the capacitorC2. The connection 512 of the capacitor C2 is connected to theconnection 503 of the input and output, to the anode of the diode D1, tothe source input of the MOSFET V2, to the connection 526 of thecapacitor C1, and to the connection 515 of the auxiliary winding L1T2 ofthe inductance L1. The connection 516 of the auxiliary winding L1T2 isconnected to the anode of the diode D2 and to the positive input of thecomparator Komp1. The negative input of the comparator Komp1 isconnected to the reference voltage U1. The cathode of the diode D2 isconnected to the connection 523 of the resistor R2 while the connection524 of the resistor R2 is connected to the connection 525 capacitor C1,to the drain connection of the MOSFET V2, to the connection 522 of theresistor R1, and to the positive input of the comparator Komp2. Theconnection 521 of the resistor R1 is connected to the reference voltageU2. The output of the control voltage unit 530 is connected to thenegative input of the comparator Komp2. The output of the comparatorKomp2 is connected to the RESET input of the pulse width modulation 510.

Operation of the Circuit According to FIG. 5:

The reference voltages U1 and U2 are preferably generated by a voltagedivider (not shown). The driver 520 preferably functions to achieve apotential-free triggering of the MOSFET V1.

The comparator Komp1 is used for demagnetization detection as describedin conjunction with FIG. 4. The resistor R2 and capacitor C1 are used incombination with the auxiliary winding L1T2 for balancing the current bymeans of the primary winding L1T1 of the inductance L1. Preferably, thelow-pass comprised of the resistor R2 and capacitor C1 has asignificantly higher frequency 1/τ, whereτ=R2*C1than the operating frequency of the buck converter (typically fromapprox. 20 KHz to 200 KHz). As a result, the voltage at the capacitor C1increases in accordance with the current. An overlay with acurrent-dependent time element R1C1 occurs, i.e. the charging of thecapacitor C1 is dependent on both the input voltage-proportional signal(via the auxiliary winding L1T2) and the reference voltage U2.

If the MOSFET V1 is switched off, then the MOSFET V2 is triggered anddischarges the capacitor C1.

As opposed to the depiction in FIG. 4, FIG. 5 shows a common negativepotential shared by the input and output. By contrast with FIG. 4,instead of measuring the current flowing through the inductance L1, thecurrent signal is determined through an integration of the voltage inthe inductance L1. The overlaying with the saw tooth signal occursthrough integration of a reference voltage U2.

FIG. 6 shows another circuit diagram of a buck converter with atriggering of an electronic circuit and corresponds in many parts to thedepiction in FIG. 5. In lieu of the reference voltage U2, FIG. 6 shows apeak value rectifying unit 610 with an input 601, an output 602, and adiode D3.

The anode of the diode D3 is connected to the anode of the diode D2, tothe connection 516 of the auxiliary winding L1T2, and to the positiveinput of the comparator Komp1. The cathode of the diode D3 is connectedto the input 601 of the peak value rectifier 610, while the output 602of the peak value rectifier 610 is connected to the connection 521 ofthe resistor R1. The reference voltage U2 (from FIG. 5) is eliminated.

Operation of the Circuit According to FIG. 6:

In addition to the explanations made in conjunction with FIG. 5, thepeak value rectifier 610 is provided in FIG. 6. Preferably, the voltageof the inductance L1 via the auxiliary winding L1T2 is rectified with aretention time constant that is greater than a line period (when thecircuit is used in a power supply, in particular a switched mode powersupply). This limits the peak current of the current flowing through theinductance, independent of the line voltage. In particular, theretention time constant can be (significantly) greater than five timesthe line period.

FIG. 7 shows another circuit diagram of a buck converter with atriggering of an electronic circuit and corresponds in many parts to thedepiction in FIG. 6. In FIG. 7, an additional peak value rectifier 710is provided, with an input 701 and an output 702.

Instead of the cathode of the diode D2 being connected to the connection523 of the resistor R2 as in FIG. 6, in FIG. 7, the cathode of the diodeD2 is connected to the input 701 of the peak value rectifier 710. Theoutput 702 of the peak value rectifier 710 is connected to theconnection 523 of the resistor R2.

Operation of the Circuit According to FIG. 7:

In lieu of the direct integration of the voltage (for current balancing)in the inductance L1 (determined via the auxiliary winding L1T2) as inFIG. 5 or FIG. 6, in FIG. 7, an additional peak value rectification isperformed, in particular with a significantly lower retention timeconstant than the line period (e.g. ⅕ the line period). Theadvantageously suppresses undesirable interactions with precedingcomponents and/or with the line impedance.

FIG. 8 shows another circuit diagram of a buck converter with atriggering of an electronic circuit and corresponds in many parts to thedepiction in FIG. 7. In FIG. 8, a reference voltage U3 and a diode D4are also provided.

The reference voltage U3 contacts the anode of the diode D4, while thecathode of the diode D4 is connected to the cathode of the diode D3 andto the input 601 of the peak value rectifier 610.

FIG. 9 shows another circuit diagram of a buck converter with atriggering of an electronic circuit and corresponds in many parts to thedepiction in FIG. 7. In FIG. 9, a reference voltage U3 and a comparatorKomp3 are also provided.

The positive input of the comparator Komp3 is connected to the positiveinput of the comparator Komp1, to the anode of the diode D3, to theanode of the diode D2, and to the connection 516 of the auxiliarywinding L1T2. The negative connection of the comparator Komp3 isconnected to the reference voltage U3. The output of the comparator isconnected to an (additional) RESET input of the pulse width modulation510.

Operation of the Circuit According to FIGS. 8 and 9:

With very small differences between the input voltage and the outputvoltage, the voltage via the inductance L1 can fall to zero and thecurrent through the inductance can no longer increase. This effect canoccur, for example, when a radio interference filter precedes thecircuit and can be due to the impedance of this radio interferencefilter and/or the line impedance.

In order to prevent excessively long switch-on times and thus theexcitation of undesirable modes (harmonics), particularly due to acurrent modulation with subharmonics of the switching frequency, theswitch-on duration is limited in that a minimum value of the voltage inthe peak value memory of the peak value rectifier 610 is predeterminedin conjunction with the reference voltage U3 (see FIG. 8).

Alternatively, the voltage in the inductance L1 can be monitored andwhen it falls below a predetermined threshold (minimum value), adisconnection can be executed (see FIG. 9).

FIG. 10 shows another circuit diagram of a buck converter with atriggering of an electronic circuit and corresponds in many parts to thedepiction in FIG. 9. In FIG. 10, a driver 1010 (with an input 1012 andan output 1013), a resistor R3 (with connections 1014 and 1015), and ann-channel MOSFET V3 are provided. In addition, the pulse widthmodulation 510 has an additional output 1011. The diode D1 is eliminatedand is replaced by the MOSFET V3 and the resistor R3.

The negative input of the comparator Komp1 is connected to the sourceconnection of the MOSFET V3 and to the connection 1014 of the resistorR3. The positive connection of the comparator Komp1 is connected to thereference voltage U1. The output of the comparator Komp1 (unchanged fromFIG. 9) is connected to the SET input of the pulse width modulation 510.The output 1011 of the pulse width modulation 510 is connected to theinput 1012 of the driver 1010, while the output 1013 of the driver 1010is connected to the gate connection of the MOSFET V3. The drainconnection of the MOSFET V3 is connected to the source connection of theMOSFET V1 and to the connection 513 of the primary winding L1T1 of theinductance L1. The remaining connection 1015 of the resistor R3 isconnected to the connection 503 (negative pole) of the input and output,to the connection 512 of the capacitor C2, to the source connection ofthe MOSFET V2, to the connection 526 of the capacitor C1, and to theconnection 515 of the auxiliary winding L1T2.

Operation of the Circuit According to FIG. 10:

In the circuit according to FIG. 10, the diode D1 is replaced by theMOSFET V3 (and the resistor R3). This achieves an additional reductionin the switching losses, particularly if the input voltage is greaterthan the output voltage (overload). The signal for switching-off theMOSFET V3 and the (delayed) switching-on of the MOSFET V1 (SET signal atthe pulse width modulation 510) is derived from the magnitude of thereverse current, measured by means of the resistor R3 and combined viathe comparator Komp1. It is optionally possible to carry out controlinterventions in the MOSFETs V1 and V2.

It should also be noted that the comparators shown above and mentionedin conjunction with the figures can also be replaced by transistors,e.g. bipolar or field effect transistors.

1. A buck converter comprising: an input with a first connection (101)and second connection (102), an output with a first connection (103) andsecond connection (104), a switch (110), a diode (D1) having a cathodeand an anode an inductance (L1), a capacitor (C1), wherein the firstconnection (101) of the input is connected to the first connection (103)of the output via a series circuit comprised of the switch (110) and theinductance (L1), the cathode of the diode (D1) is connected to theconnection between the switch (110) and the inductance (L1), the anodeof the diode (D1) is connected to the second connection (102) of theinput and to the second connection (104) of the output, and thecapacitor (C1) is connected in parallel with the connections (103, 104)of the output, such that the switch (110) is triggered from a firststate to a second state by combining a first signal with a secondsignal, wherein the switch is triggered by combining the first signalwith the second signal and a third signal, wherein the second signal isan essentially triangular shaped signal generated by a saw toothgenerator, and means for adding the current signal and the essentiallytriangular shaped signal by integration of a voltage in the inductance(L1) and an additional voltage.
 2. The buck converter as recited inclaim 1, wherein the first connection (101) of the input is of apositive polarity and the second connection (102) of the input is of anegative polarity.
 3. The buck converter as recited in claim 1, whereinthe third signal is a control variable from the output of the buckconverter and is used to adjust the output signal of the buck converterand is substantially constant.
 4. The buck converter as recited in claim1, further including means for regulating, wherein the third signal isadjustable or controllable by at least one predetermined parameterselected from among an output voltage of the buck converter, an outputcurrent of the buck converter, and a power of the buck converter.
 5. Thebuck converter as recited in claim 1, wherein the switch (110) comprisesat least one electronic switch.
 6. The buck converter as recited inclaim 1, wherein the diode (D1) is embodied in the form of an electronicswitch.
 7. The buck converter as recited in claim 5, wherein said atleast one electronic switch is selected from the group comprising atransistor or at least one MOSFET, at least one thyristor, and at leastone IGBT.
 8. The buck converter as recited in claim 1, wherein theswitch is triggered by a signal representing the sum of the first signaland the second signal.
 9. The buck converter as recited in claim 8,wherein the sum of the first signal and the second signal is compared tothe third signal.
 10. The buck converter as recited in claim 1, whereinthe first signal is a current signal that corresponds to the currentthrough the electronic switch (110).
 11. The buck converter as recitedin claim 1, further including means for determining the additionalvoltage by peak value rectification of the voltage in the inductanceusing a retention time constant that is, in particular, greater than theline period.
 12. The buck converter as recited in claim 11 furtherincluding means for an additional peak value rectification using aretention time constant that is less than the line period.
 13. The buckconverter as recited in claim 1, further including means for limiting ontime duration of the switch (110) if the voltage in the inductance fallsbelow a predeterminable minimum voltage.
 14. The buck converter asrecited in claim 13, wherein an online duration of the switch (110) islimited when the voltage in the inductance falls below thepredeterminable minimum voltage.
 15. A buck converter, comprising: aninput with a first connection (101) and second connection (102); anoutput with a first connection (103) and second connection (104); aswitch (110); a diode (D1) having a cathode and an anode; an inductance(L1); a capacitor (C1); wherein the first connection (101) of the inputis connected to the first connection (103) of the output via a seriescircuit comprised of the switch (110) and the inductance (L1); the anodeof the diode (D1) is connected to the connection between the switch(110) and the inductance (L1), the cathode of the diode (D1) isconnected to the second connection (102) of the input and to the secondconnection (104) of the output, and the capacitor (C1) is connected inparallel with the first and second connections (103, 104) of the output,and such that the switch (110) is triggered from a first state to asecond state by combining a first signal with a second signal, whereinthe switch is triggered by combining the first signal with the secondsignal and a third signal, wherein the second signal is an essentiallytriangular shaped signal generated by a saw tooth generator, and meansfor adding the current signal and the essentially triangular shapedsignal by integration of a voltage in the inductance (L1) and anadditional voltage.
 16. The buck converter as recited in claim 15,wherein the first connection (101) of the input is of a negativepolarity and the second connection 102 of the input is of a positivepolarity.
 17. The buck converter as recited in claim 15, wherein thethird signal is a control variable from the output of the buck converterand is used to adjust the output signal of the buck converter and issubstantially constant.
 18. The buck converter as recited in claim 15,further including means for regulating, wherein the third signal isadjustable or controllable by at least one predetermined parameterselected from among an output voltage of the buck converter, an outputcurrent of the buck converter, and a power of the buck converter. 19.The buck converter as recited in claim 15, wherein the switch (110)comprises at least one electronic switch.
 20. The buck converter asrecited in claim 15, wherein the diode (D1) is embodied in the form ofan electronic switch.
 21. The buck converter as recited in claim 20,wherein said at least one electronic switch is selected from the groupcomprising a transistor or at least one MOSFET, at least one thyristor,and at least one IGBT.
 22. The buck converter as recited in claim 15,wherein the switch is triggered by a signal representing the sum of thefirst signal and the second signal.
 23. The buck converter as recited inclaim 22, wherein the sum of the first signal and the second signal iscompared to the third signal.
 24. The buck converter as recited in claim15, wherein the first signal is a current signal that corresponds to thecurrent through the electronic switch (110).
 25. The buck converter asrecited in claim 15, further including means for determining theadditional voltage by peak value rectification of the voltage in theinductance using a retention time constant that is, in particular,greater than the line period.
 26. The buck converter as recited in claim25, further including means for an additional peak value rectificationusing a retention time constant that is less than the line period. 27.The buck converter as recited in claim 15, further including means forlimiting on time duration of the switch (110) if the voltage in theinductance falls below a predeterminable minimum voltage.
 28. The buckconverter as recited in claim 27, wherein an online duration of theswitch (110) is limited when the voltage in the inductance falls belowthe predeterminable minimum voltage.